fn main() {
    let mut s1 =  String::from("abcde");
    let mut s2 =  String::from("aaa");
    let r = longest(&s1, &s2);
    println!("r={}", r);

}

fn longest<'a>(x: &'a String, y: &'a String) -> &'a String {
    return if x.length() > y.length() {
        &x
    } else {
        y
    }
}
